Set SKIP_FIRST_USE_HINTS setting for private space

With this change the value of Secure settings SKIP_FIRST_USE_HINTS is
set for private profile after creation of profile in PS setup flow.

The value is set for the profile user so that first launch of an app in
private space will not display introductory hints.

Bug: 325596557
Test: PrivateSpaceMaintainerTest
Change-Id: I63a967bba052a3dcb4742c95b89c6da19aba74d5